AM3352: Random processor failures

Andrew Malaniak

Part Number: AM3352
Other Parts Discussed in Thread: TPS65217

Hello:

We are experiencing random processor failures using AM3352BZCZD80.

It is being powered by the recommended PMIC TPS65217. These failures seem to occur upon startup and they seem to never recover.

The PMIC output VLOD4 PIN 43 3.3 V and all other outputs get pulled down to zero when these failures occur. This output supplies many of the voltage supply rails of the processor.

When we uncouple the load to this particular output (VLOD4) by removing a series zero Ohm resistor, the PMIC then becomes active again with all voltage rails supplying the correct voltages.

We have theorized that something has shorted in the processor. We have virtually no way to forensically investigate these processors.

What we are looking for is some insight into why this is happening, and if there are some design considerations that we need to address.

Thank You

Andy

over 6 years ago

0 Brian Berner over 6 years ago

TI__Mastermind 30310 points

Andy,

As you mentioned, the PMIC LDO4 output works as expected when you isolate it from the load by removing 0-Ohm resistor, so I think the PMIC is working as expected.

Currently, this question is assigned to the Processor team, and I will leave it this way for now unless someone can identify an issue with the PMIC.

0 Biser Gatchev-XID over 6 years ago in reply to Brian Berner

TI__Guru**** 393215 points

Hi Andy,

From processor side one possible cause of failure can be when an external voltage is present on an AM335x I/O pin while the processor is powered off. AM335x I/O pins are not fail-safe (with the exception of USBx_VBUS pins). See the parameter "Steady state max voltage
at all I/O pins" in section 5.1 of the AM335x Datasheet Rev. K, and also check Note 8 after the table.

0 Andrew Malaniak over 6 years ago in reply to Biser Gatchev-XID

Prodigy 20 points

Hi. Thanks for the tips and a direction to follow. What if these residual voltages on the I/O pins are at acceptable levels? I would assume that the safest condition to boot the processor is when all inputs and outputs are at zero with no residual charge.

0 Biser Gatchev-XID over 6 years ago in reply to Andrew Malaniak

TI__Guru**** 393215 points

If the external voltages are within the range -0.5V to +0.3V when all processor power supplies are at 0V, there will be no damage.

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AM3352: Random processor failures